Triple radius bourdon tube



United. States Patent 9 TRJPLE RADIUS BQURDGN TUBE Lowell E. Linden, Los- Angeles, Calif., assignor of one- This invention relates to pressure-sensitive devices and is particularly directed to improvements in Bourdon tubes.

Bourdon tubes of conventional type are C shapedin outline. They have one end fixed and the other end free to move. Changes in internalpressure applied at the fixed end cause the free end to move through a path of travel. Such conventional Bourdon tubes are satisfactory' for many applications but have been found unsatisfactory when subjected to high acceleration or deceleration forces or when fixed on vibrating or oscillating mounts. Moreover such conventional Bourdon tubes have a. rather high temperature correction factor, high hysteresis lag and low power output. Furthermore, they are incapable of producing straight linear movement proportional to changes in pressure.

It is the principal object of my invention to provide an improved form of- Bourdon tube which eliminates or minimizes these shortcomings.

An important object of my invention is to provide a pressure-sensitive tube of the Bourdon type having both ends fixed.

Another object is to provide an improved Bourdon tube of this type which is relatively unaffected by high acceleration and deceleration forces.

Another object is to provide an improved Bourdon tube of this type having a high natural frequency of vibration.

Aonther important object is. to' provide an improved type Bourdon tube which generates astraight-line' linear movement in proportion to changes in pressure.

Other objects and advantages will appear hereinafter.

In the drawings: 7 V

Figure 1 is a plan view showing a preferred ernbodiment of my invention.

Figure 2 is a sectional elevation taken substantially on the lines 22 as shown in Figure 1.

Figure 3 is a transverse sectional view taken substantially on the lines 33 as shown in Figure 2.

Figure 4 is a transverse sectional view showing a modified form of my invention.

Figure 5 is a sectional view showing a further modification.

Figures 6, 7 and 8 are diagrammatic illustrations showing various modifications of my invention.

Referring to the drawings, the pressure-sensitive tube generally designated 10 is provided with three separate curved portions 11, 12 and 13. The ends 14 and 15 of the tube are fixed with respect to the mounting block 16. The tube 10 may have any of the cross sections which are well known for Bourdon tubes and, as shown in Figure 3, may comprise a flattened oval having substantially concentric outer and inner walls 17 and 18, respectively. The ends of the tube may be secured to the mounting block 16 by any means that provides a secure connection and a pressure tight joint. I have found that a brazed connection gives satisfactory results. The ends Ere.

of the tube Ill-communicate through passages 19 with the central opening-20 within the block 16'. The pipe 21 has athreaded connection 22 with the block 16 and serves to pressurize the interior of the tube 10.

The curved portions 11 and 13 have equal radii 23 and 24 and the ends 14 and 15 are coaxial. The central curved portion 12 constitutes a reverse bend and its radius 25 is made equal to the radii 23 and 24. A post 26, or other attachment element, is fixed centrally to the curved portion 12. The device is symmetrical. about a center line passing along the axis of thepost 26.

When pressure is admitted into the interior of the tube 10 from the pipe 21, the curved portions 11, 12 and 13 each tend to straighten out. Since the tube 10 is formed of uniform stock and since the curved sections 11 and 13 are identical, they'transrnit similar forces to the curved section12. Since all threesections 11 12 and 13 tend to straighten out when the tube is pressurized, the post 26 moves. axially in a direction awayfrom the block: 16. The motion of the post is linear and not arcuate. Furthermore, Within the limits of operating pressure, the extent. of movement of the post is directly proportional to the increase in pressure. This straight line motion is highly desirable for many applications. It has been found particularly useful for actuation of indicating, recording or switching devices.

In the form of. my invention shown in Figure 4, the mounting piece 30 comprises an elongated member having a central bore 31. The tube 32 has its ends 33 and 34 fixed to the mounting piece 30,. as by brazing. The curved portions 35' and 36 of. the tube are substantially identical and have the same radius of' curvature as the central reverse bend 37. The post 33 is fixed centrally of the curved portion'37. The device operates in substantially the same manner. as describedabove but. has a shorter range of travel. because the outer curved portions have a shorter arcuate length.

Conventional C shaped Bourdon tubes. havingone end closed are difficult to flush out. In certain types of install'ations where short life of the parts. is permissible, stainless steel tubes are employed with nitric acid as the hydraulic liquid. In test workv to determine the operating characteristics of such a device, and for other reasons, it may be necessary or desirable.- to flush out. the nitric acid after a test in order topreserve the tube for further testwork. The device shown in Figure 4 permits flushing of the interior of the tube 32 to clean out the contentsthereof. This may be accomplished byremoving the threaded plug 40 and attaching a hydraulic inlet fitting in the threads which normally receive the plug 40. Flushing fluid can then be passed through the tube to clean it.

in that form of my invention shown in Figure 5, the curved portions 46 and 41 of the Bourdon tube 42 are relatively long in arcuate length. The reverse bend portion 43 is substantially the same as that shown in Figures 2 and 4. The ends 44 and 45 of the tube 42 are fixed to the mounting block 46 in any suitable manner, as by brazing. The important advantage of this construction is that it provides a relatively long stroke for the post 47. The pipe 48 communicates with the interior of the Bourdon tube 42 through the port 49 and end 45 of the tube 42. If desired, a similar port could be provided in the block 46 for connecting the pipe 48 with the ends 44 of the tube 42. It is desirable that both ends of the tube 42 be anchored but either one or both ends can be connected to the pressure source.

The three curved portions of the tube embodying my invention preferably have the same radius of curvature when it is desired that the post have a straight line motion. However, my invention is not limited to equal radius curves but on the contrary special applications and design techniques may require that the central reverse an arrangement in which the two side curves have an equal radius but wherein the center reverse curve has "a smaller radius. Figure 7 shows a construction in which the center reverse curve has a larger radius. The effect of increasing the radius of the center reverse curve is to increase the range of travel of the actuating element.

In Figure 8 I have diagrammatically shown a Bourdon tube embodying my invention and which uses three different radii for the three curved portions of the tube. Such an arrangement is used when it is desired to have the central post 50 moved in a curved path of predetermined shape whenever pressure is applied to the interior of the tube 51. In certain cases it is desirable to have the actuating element 50 move in a curved path to compensate for certain characteristics in the driven mechanism. The greater the difference in curvature of the two ections 52 and 52, the greater is the curvature of the path of movement of the actuating element 50. As is seen in Fig. 8 of thedrawings, the area embraced by the portion having the reverse curve is separate and distinct and does not overlap the areas embraced by theportions of the tube device having an unequal radius of curva ture.

One of the outstanding advantages of each of the types ofpressure-sensitive tubes shown in the drawings is that a much higher operating force is developed than is possibleto obtain with the conventional C-shaped Bourdon tube.

' Having fully described my invention, it is to be understood that I do not wish to be limited to the details 7 herein set forth but my invention is of the full scope'of the appended claims.

I claim:

' l. A pressure-sensitive tube device of the Bourdon type 7 comprising a single length of tubing noncircular in cross section, a mounting member, means fixing both ends of' the tubing. to the mounting member, the tubing having a pair of curved portions of unequal radius of curvature adjacent the ends of the tubing and having a reverse curved portion connecting the two first-said portions, the area embraced by the portion having the reverse curve being separate and distinct and not overlapping the area embraced by either of the said portions having unequal radius of curvature, said portion having the reverse curve including a location for reception of an actuator, andport 'means in the mounting member for pressurizing the interior of the tube.

2. A pressure-sensitive tube of the Bourdon type having a pair of duplicate arcuate portions of constant radius adjacent the ends of the tube, a mounting member, means fixing both ends of the tube to the mounting member, said portions being connected by a central reverse curved portion of constant radius, the latter said portion including a location for reception of an actuator, the tube beingsymmetrical about an axis passing through the actuator element.

3. A pressure-sensitive tube device of the Bourdon type comprising a single length of tubing non-circular in cross section, a mounting member, means fixing both ends of the tubing to the mounting member, the tubing having a pair of curved portions of substantially equal radius of curvature adjacent the ends of the tubing and having a reverse curved portion connecting the two first-said portions, the portion having the reverse curve including a location for reception of an actuator, and port means in the mounting member for pressuriz'ing the interior of the tubing.

4. The device set forth in claim 3 in which the radius of curvature of the reverse curved portion is substantially equal to that of the other portions.

5. The device set forth in claim 3 in which the radius of curvature of the reverse curved portion is substantially less than that of the other portions.

6. The device set forth in claim 3 in which the radius of curvature of the reverse curved portion is substantially greater than that of the other portions.

7 7. A pressure-sensitive tube device of the Bourdon type comprising a single length of tubing non-circular in cross section, a mounting member, means fixing both ends of the tubing to the mounting member, the tubing having a pair of curved portions of substantially equal radius of curvature adjacent the ends of the tubing and having a reverse curved portion connecting the two first-said portions, the portion having the reverse curve including 7 References Cited in the file of this patent UNITED STATES PATENTS 50,208 Schmidt l. Sept. 26, 1865. 731,585 Manning June 23, 1903 1,595,749 Andersen Aug. 10, 1926 2,470,714 Nevius May 17, 1949 2,526,124 Dobson et a1 Oct. 17, 1950 FOREIGN PATENTS 86,736 Germany May 6, 1896 111,614 Germany July 6, 1900 

